Crdm internal electrical connector

ABSTRACT

An internal control rod drive mechanism (CRDM) including an electric motor is disposed in a nuclear reactor and further includes a support surface with sealed electrical connectors electrically connected with the electric motor power the motor. The internal CRDM is disposed on a support element secured inside the nuclear reactor. The support element includes sealed electrical connectors mating with the sealed electrical connectors on the support surface of the internal CRDM to power the electric motor. The sealed electrical connectors may be sealed glass, ceramic, or glass-ceramic connectors welded onto the ends of the MI cables extending from the motor. Springs, are disposed between the mating sealed electrical connectors of the support element and the support surface. A purge line is integrated with each mated connection.

CLAIM OF PRIORITY

This application is a division of U.S. application Ser. No. 13/863,611filed Apr. 16, 2013, now U.S. Pat. No. 9,911,512, which is acontinuation-in-part of U.S. application Ser. No. 13/405,405 filed Feb.27, 2012, now U.S. Pat. No. 9,805,832, which claims the benefit of U.S.Provisional Application No. 61/625,484 filed Apr. 17, 2012, whichapplications are hereby incorporated by reference in their entirety.

BACKGROUND

The following relates to the nuclear reactor arts, nuclear powergeneration arts, nuclear reactor control arts, nuclear reactorelectrical power distribution arts, and related arts.

In nuclear reactor designs of the integral pressurized water reactor(integral PWR) type, a nuclear reactor core is immersed in primarycoolant water at or near the bottom of a pressure vessel. In a typicaldesign, the primary coolant is maintained in a subcooled liquid phase ina cylindrical pressure vessel that is mounted generally upright (thatis, with its cylinder axis oriented vertically). A hollow cylindricalcentral riser is disposed concentrically inside the pressure vessel.Primary coolant flows upward through the reactor core where it isheated, rises through the central riser, discharges from the top of thecentral riser, and reverses direction to flow downward back toward thereactor core through a downcomer annulus.

The nuclear reactor core is built up from multiple fuel assemblies. Eachfuel assembly includes a number of fuel rods. Control rods comprisingneutron absorbing material are inserted into and lifted out of thereactor core to control core reactivity. The control rods are supportedand guided through control rod guide tubes which are in turn supportedby guide tube frames. In the integral PWR design, at least one steamgenerator is located inside the pressure vessel, typically in thedowncomer annulus, and the pressurizer is located at the top of thepressure vessel, with a steam space at the top most point of thereactor. Alternatively an external pressurizer can be used to controlreactor pressure.

A set of control rods is arranged as a control rod assembly thatincludes the control rods connected at their upper ends with a spider,and a connecting rod extending upward from the spider. The control rodassembly is raised or lowered to move the control rods out of or intothe reactor core using a control rod drive mechanism (CRDM). In atypical CRDM configuration, an electrically driven motor selectivelyrotates a roller nut assembly or other threaded element that engages alead screw that in turn connects with the connecting rod of the controlrod assembly. The control rods are typically also configured to “SCRAM”,by which it is meant that the control rods can be quickly released in anemergency so as to fall into the reactor core under force of gravity andquickly terminate the power-generating nuclear chain reaction. Towardthis end, the roller nut assembly may be configured to be separable soas to release the control rod assembly and lead screw which then falltoward the core as a translating unit. In another configuration, theconnection of the lead screw with the connecting rod is latched andSCRAM is performed by releasing the latch so that the control rodassembly falls toward the core while the lead screw remains engaged withthe roller nut. See Stambaugh et al., “Control Rod Drive Mechanism forNuclear Reactor”, U.S. Pub. No. 2010/0316177 A1 published Dec. 16, 2010which is incorporated herein by reference in its entirety; and DeSantis,“Control Rod Drive Mechanism for Nuclear Reactor”, U.S. Pub. No.2011/0222640 A1 published Sep. 15, 2011 which is incorporated herein byreference in its entirety.

The CRDMs are complex precision devices which require electrical powerto drive the motor, and may also require hydraulic, pneumatic, oranother source of power to overcome the passive SCRAM release mechanism(e.g., to hold the separable roller nut in the engaged position, or tomaintain latching of the connecting rod latch) unless this is alsoelectrically driven. In existing commercial nuclear power reactors, theCRDMs are located externally, i.e. outside of the pressure vessel,typically above the vessel in PWR designs, or below the reactor inboiling water reactor (BWR) designs. An external CRDM has the advantageof accessibility for maintenance and can be powered through externalelectrical and hydraulic connectors. However, the requisite mechanicalpenetrations into the pressure vessel present safety concerns.Additionally, in compact integral PWR designs, especially thoseemploying an internal pressurizer, it may be difficult to configure thereactor design to allow for overhead external placement of the CRDMs.Accordingly, internal CRDM designs have been developed. See U.S. Pub.No. 2010/0316177 A1 and DeSantis, “Control Rod Drive Mechanism forNuclear Reactor”, U.S. Pub. No. 2011/0222640 A1 published Sep. 15, 2011which is incorporated herein by reference in its entirety. However,placing the CRDMs internally to the reactor vessel requires structuralsupport and complicates delivery of electrical and hydraulic power.Electrical conductors, which may be Mineral Insulated (MI) cable, thatare usable inside the pressure vessel are generally not flexible and arenot readily engaged or disengaged, or spliced, making installation andservicing of internal CRDM units time consuming and labor-intensive.

Disclosed herein are improvements that provide various benefits thatwill become apparent to the skilled artisan upon reading the following.

BRIEF SUMMARY

In some illustrative embodiments, an apparatus comprises: a nuclearreactor including a pressure vessel and a nuclear reactor corecomprising fissile material disposed in the pressure vessel; an internalcontrol rod drive mechanism (CRDM) including an electric motor disposedin the pressure vessel and a support surface including sealed electricalconnectors electrically connected with the electric motor to deliverelectrical power to the electrical motor; and a support element securedinside the pressure vessel on which the support surface of the internalCRDM is disposed to support the internal CRDM in the pressure vessel,the support element including sealed electrical connectors mating withthe sealed electrical connectors on the support surface of the internalCRDM to deliver electrical power to the electric motor of the internalCRDM. In some embodiments the internal CRDM further comprises mineralinsulated cables (MI cables) electrically connecting the electric motorto the sealed electrical connectors on the support surface, wherein eachMI cable is connected to one of the sealed electrical connectors and thesealed electrical connectors are sealed glass connectors, sealed ceramicconnectors, or sealed glass ceramic connectors. In some embodiments thesealed electrical connectors and the sealed electrical connectors arewelded onto the ends of the MI cables. In some embodiments springs, e.g.wave springs, are disposed between the sealed electrical connectors ofthe support element and the mating sealed electrical connectors on thesupport surface of the internal CRDM. In some embodiments a purge lineis integrated with each mated connection of a sealed electricalconnector of the support element and the mated sealed electricalconnector on the support surface of the internal CRDM. The internal CRDMmay include a standoff mechanically secured with the internal CRDM, thesupport surface of the internal CRDM being a surface of the standoff.The support element may comprise a distribution plate including MIcables disposed on or in the distribution plate and terminating at thesealed electrical connectors of the distribution plate.

In some illustrative embodiments, a method comprises providing aninternal control rod drive mechanism (CRDM) including an electric motorand a support surface including sealed electrical connectorselectrically connected with the electric motor to deliver electricalpower to the electrical motor, and installing the internal CRDM inside anuclear reactor, the installing including placing the support surface ofthe internal CRDM onto a support element inside the nuclear reactor, theplacing causing sealed electrical connectors disposed on the supportelement to mate with the sealed electrical connectors on the supportsurface of the internal CRDM. In such a method, the nuclear reactor maycontain coolant water and the installing may be performed with theinternal CRDM submerged in the coolant water—the seals of the sealedelectrical connectors of the internal CRDM and the support element areeffective to prevent coolant water ingress into the sealed electricalconnectors. The method may further comprise, after the placing isperformed, purging space between the mated sealed electrical connectorsof the internal CRDM and the support element through a purge line usingan inert gas. Still further, the method may comprise sealing off thepurge line after the purging in order to trap residual inert gas in thespace between the mated sealed electrical connectors of the internalCRDM and the support element.

In some illustrative embodiments, an internal control rod drivemechanism (CRDM) includes as a unitary assembly: an electric motor; asupport surface; sealed glass, ceramic, or glass ceramic electricalconnectors disposed on the support surface; and MI cables extending fromthe electric motor and having ends sealed inside the sealed glass,ceramic, or glass ceramic electrical connectors. The seals of the sealedglass, ceramic, or glass-ceramic electrical connectors are effective toallow the internal CRDM to be immersed in water without water ingressinto the MI cables. Optionally, each sealed glass, ceramic, orglass-ceramic electrical connector further includes a purge linearranged to admit purge gas into space between the sealed glass,ceramic, or glass-ceramic electrical connector and an associated matingconnector.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take form in various components and arrangements ofcomponents, and in various process operations and arrangements ofprocess operations. The drawings are only for purposes of illustratingpreferred embodiments and are not to be construed as limiting theinvention.

FIG. 1 diagrammatically shows an integral pressurized water reactor(integral PWR) with the upper internals of the reactor inset.

FIG. 2 shows a perspective view of a distribution plate suitably used inthe upper internals of the integral PWR of FIG. 1.

FIG. 3 is a detail of one of the openings of the distribution plate ofFIG. 2.

FIG. 4 illustrates a perspective view of a standoff assembly formounting on the distribution plate of FIG. 2.

FIG. 5 illustrates a view of the standoff assembly of FIG. 4 from adifferent perspective.

FIG. 6 illustrates the standoff assembly of FIGS. 4 and 5 connected to aControl Rod Drive Mechanism (CRDM) with associated electrical andhydraulic cabling.

FIG. 7 is a cutaway view of an electrical connection between thestandoff assembly and the distribution plate.

FIG. 8 is the male connector of FIG. 7 shown removed from thedistribution plate.

FIG. 9 is an alternative embodiment of the connector shown installed inthe standoff assembly of FIGS. 4 and 5.

FIG. 10 is a cutaway of the connector of FIG. 9.

FIGS. 11 and 12 show exploded and assembled perspective views,respectively, of connectors of FIGS. 9 and 10.

FIG. 13 illustrates a method of connecting a CRDM with standoff assemblyto a distribution plate.

FIG. 14 illustrates a method of removing a CRDM and standoff assemblyfrom a distribution plate.

FIG. 15 diagrammatically shows an overhead view of a pump plate withinternal reactor coolant pumps (RCP's) mounted in most openings.

FIG. 16 diagrammatically shows a perspective view of one of the RCPs ofFIG. 15.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates an integral Pressurized Water Reactor (integral PWR)generally designated by the numeral 10. A reactor vessel 11 is generallycylindrical and contains a nuclear reactor core 1 comprising fissilematerial (e.g. ²³⁵U), steam generators 2, and a pressurizer 3. Althoughan integral pressurized water reactor (PWR) is depicted, embodimentsutilizing a boiling water reactor (BWR), PWR with external steamgenerators, or other type of nuclear reactor are also contemplated.Moreover, while the disclosed rapid installation and servicingtechniques are described with reference to illustrative internal CRDMunits, these techniques are readily adapted for use with other internalnuclear reactor components such as internal reactor coolant pumps.

In the illustrative PWR, above the core 1 are reactor upper internals 12of integral PWR 10, shown in inset. The upper internals 12 are supportedlaterally by a mid-flange 14, which in the illustrative embodiment alsosupports internal canned reactor coolant pumps (RCPs) 16. Moregenerally, the RCPs may be external pumps or have other configurations,and the upper internals may be supported otherwise than by theillustrative mid flange 14. The upper internals include control rodguide frames 18 to house and guide the control rod assemblies forcontrolling the reactor. Control Rod Drive Mechanisms (CRDMs) 20 raiseand lower the control rods to control the reactor. In accordance withone embodiment, a CRDM distribution plate 22 supports the CRDMs andprovides power and hydraulics to the CRDMs.

Control rods are withdrawn from the core by CRDMs to provide enoughpositive reactivity to achieve criticality. The control rod guide tubesprovide space for the rods and interconnecting spider to be raisedupward away from the reactor core. The CRDMs 20 require electric powerfor the motors which move the rods, as well as for auxiliary electricalcomponents such as rod position indicators and rod bottom sensors. Insome designs, the force to latch the connecting rod to the lead screw,or to maintain engagement of the separable roller nut, is hydraulic,necessitating a hydraulic connection to the CRDM. To ensure passivesafety, a positive force is usually required to prevent SCRAM, such thatremoval of the positive force initiates a SCRAM. The illustrative CRDM20 is an internal CRDM, that is, is located inside the reactor vessel,and so the connection between the CRDM 20 and the distribution plate 22is difficult to access. Servicing of a CRDM during a plant shutdownshould preferably be rapid in order to minimize the length of theshutdown. To facilitate replacing a CRDM in the field, a standoffassembly connected to the distribution plate 22 to provide precisevertical placement of the CRDM 20 is also configured to provideelectrical power and hydraulics to the CRDM 20 via connectors thatrequire no action to effectuate the connection other than placement ofthe standoff assembly onto the distribution plate 22. After placement,the standoff is secured to the distribution plate by bolts or otherfasteners. Additionally or alternatively, it is contemplated to relyupon the weight of the standoff assembly and CRDM to hold the assemblyin place, or to use welds to secure the assembly.

The illustrative distribution plate 22 is a single plate that containsthe electrical and hydraulic lines and also is strong enough to providesupport to the CRDMs and upper internals without reinforcement. Inanother other embodiment, the distribution plate 22 may comprise a stackof two or more plates, for example a mid-hanger plate which providesstructural strength and rigidity and an upper plate that containselectrical and/or hydraulic lines to the CRDMs via the standoffassembly.

The motor/roller nut assembly of the CRDM is generally located in themiddle of the lead screw's travel path. When the control rod is fullyinserted into the core, the roller nut is holding near the top of thelead screw, and, when the rod is at the top of the core, the roller nutis holding near the bottom of the lead screw and most of the length ofthe lead screw extends upward above the motor/roller nut assembly. Hencethe distribution plate 22 that supports the CRDM is positioned “below”the CRDM units and a relatively short distance above the reactor core.

FIG. 2 illustrates the distribution plate 22 with one standoff assembly24 mounted for illustration, though it should be understood that most orall openings 26 would have a standoff assembly (and accompanying CRDM)mounted in place during operation of the reactor. Each opening 26 allowsa lead screw of a control rod to pass through and the periphery of theopening provides a connection site for a standoff assembly that supportsthe CRDM. The lead screw passes down through the CRDM, through thestandoff assembly, and then through the opening 26. The distributionplate 22 has, either internally embedded within the plate or mounted toit, electrical power lines (e.g., electrical conductors) and hydraulicpower lines to supply the CRDM with power and hydraulics. Theillustrative openings 26 are asymmetric or keyed so that the CRDM canonly be mounted in one orientation. As illustrated, there are 69openings arranged in nine rows to form a grid, but more or fewer couldbe used depending on the number of control rods in the reactor. Thedistribution plate is circular to fit the interior of the reactor, withopenings 28 to allow for flow through the plate. In some designs, notall openings may have CRDMs mounted to them or have associated fuelassemblies.

The CRDMs are supported by the CRDM standoff assembly which is attachedto a distribution plate that provides power to the CRDMs. The connectorsfor the CRDM's are integrated into the power distribution plate assemblyand the CRDM standoff plate. They allow the disconnection of the powerand signal leads when CRDM maintenance is required without splicing MIcable.

FIG. 3 schematically illustrates a small cutaway view of one connectionsite of the distribution plate 22 for connecting a CRDM to thedistribution plate. The connection site includes an opening 26 forpassing the lead screw of a single CRDM. Located around the opening 26are apertures 40 to accept bolts (more generally, other securing orfastening features may be used) and electrical connectors 42 fordelivering electrical power to the CRDM. The illustrative CRDM employshydraulic power to operate the SCRAM mechanism, and accordingly there isalso a hydraulic connector 44 to accept a hydraulic line connection. Theopening 26 and its associated features 40, 42, 44 create a connectionsite to accept the CRDM/standoff assembly. Internal to the distributionplate 22 may be junction boxes to electrically connect the connectionsites to the electrical power lines running in between rows ofconnection sites. Similarly, the hydraulic connector 44 may connect to acommon hydraulic line running through the distribution plate separatedby depth.

FIG. 4 illustrates a standoff 24 that suitably mates to opening 26 inthe distribution plate 22. The standoff assembly has a cylindricalmidsection with plates 45, 46 of larger cross-sectional area on eitherend of the midsection. The circular top plate 45 mates to and supports aCRDM 20. The square bottom plate 46 mates to the distribution plate 22.Although the illustrative bottom plate 46 is square, it mayalternatively be round or have another shape. When the CRDM 20 and thetop plate 45 of the standoff 24 are secured together they form a unitaryCRDM/standoff assembly in which the bottom plate 46 is a flange forconnecting the assembly to the distribution plate 22. Two bolt lead-ins50 on diagonally opposite sides of the lower plate 46 mate to theapertures 40 of the distribution plate. The bolt lead-ins, being mainlyfor positioning the CRDM standoff, are the first component on thestandoff to make contact with the distribution plate when the CRDM isbeing installed, ensuring proper alignment. Two electrical powerconnectors 52 on diagonally opposite corners of the bottom plate 46 mateto corresponding electrical power connectors 42 of the distributionplate 22. Each connector 52 is installed in a raised boss or collar 53on the bottom plate 46 of the standoff 24 (e.g., see FIG. 5). Ahydraulic line connector 54 on the bottom plate 46 mates to thecorresponding hydraulic power connector 44 of the distribution plate 22.A central bore 56 of the standoff 24 aligns with the opening 26 of thedistribution plate 22 and allows the lead screw to pass through. Theconnectors 42, 44 inside the distribution plate 22 (or connectors 52, 54inside the standoff 24) optionally have internal springs to ensurepositive contact, and the opposing bolts that attach at lead-ins 50serve as tensioning devices to ensure proper seating of both the CRDMelectrical connectors and hydraulic connectors. Illustrative flow slots58 permit primary coolant to flow through the standoff.

FIG. 5 illustrates a perspective view focusing on the top plate 45 ofthe standoff 24. The top plate 45 of the standoff mates to the CRDM andis attached via bolt holes 62. Bolt holes 62 may be either threaded orunthreaded. The CRDM and standoff can be attached to each other andelectrical connections 52 and hydraulic connection 54 made before theCRDM is installed so as to form a CRDM/standoff assembly having flange46 for connecting the assembly with the connection site of thedistribution plate 22. The bottom plate 46 of the standoff 24 is securedto the connection site via bolts passing through holes 50 and secured bynuts, threads in the bolt holes 40, or the like.

FIG. 6 shows standoff 24 connected to a CRDM 20 to form a CRDM/standoffassembly that can be mounted to the distribution plate. CRDM electricalcabling 80 extends upward to conduct electrical power received at theelectrical connectors 52 to the motor or other electrical component(s)of the CRDM 20. In the embodiment of FIG. 5, each electrical connector52 terminates two electrical cables 80. Similarly, a CRDM hydraulic line82 extends upward to conduct hydraulic power received at hydraulicconnector 54 to the hydraulic piston or other hydraulic component(s) ofthe CRDM 20 to maintain latching—removal of the hydraulic powerinstigates a SCRAM. The entire assembly including the CRDM and thestandoff is then installed as a unit on a distribution plate,simplifying the installation process of a CRDM in the field.

The interface points (i.e. CRDM electrical and hydraulic connectors) inthe embodiment of FIG. 6 are at the standoff assembly but could be atany location along the length of the CRDM. For the illustrativeexamples, the interface point at which the CRDM is broken from the upperinternals is at the bottom of the CRDM. The apparatus for which theinterface points are located is the CRDM standoff and the CRDM powerdistribution plate.

In one embodiment, the electrical cables 80 are mineral insulated cables(MI cables) which generally include one, two, three, or more copperconductors wrapped in a mineral insulation such as Magnesium Oxide whichis in turn sheathed in a metal. The mineral insulation could also bealuminum oxide, ceramic, or another electrically insulating materialthat is robust in the nuclear reactor environment. MI cables are oftensheathed in alloys containing copper, but copper would corrode and havea negative effect on reactor chemistry. Some contemplated sheathingmetals include various steel alloys containing nickel and/or chromium,or a copper sheath with a protective nickel cladding.

The electrical lines in the distribution plate 22 are also suitably MIcables, although other types of cabling can be used inside thedistribution plate 22 if they are isolated by embedding in the plate. MIcables advantageously do not include plastic or other organic materialand accordingly are well suited for use in the caustic high temperatureenvironment inside the pressure vessel. The relatively rigid nature ofthe MI cables is also advantageous in that it helps ensure the integrityof the pre-assembled CRDM/standoff assembly during transport andinstallation. However, the rigidity of the MI cables limits theirbending radius to relatively large radius turns, so that the MI cablesinside the distribution plate 22 should be arranged as straight lineswith only large-radius turns. The large area of the distribution plate22, which spans a substantial portion of the inner diameter of thepressure vessel, facilitates a suitable arrangement of the MI cablesinside the plate 22. Additionally, some types of MI cables aresusceptible to degradation if the mineral insulation is exposed towater. Accordingly, the ends of the MI cables, e.g. at the coupling withthe connector 52 in the standoff and the coupling of the power lines 30with the electrical connectors 42 in the distribution plate 22, shouldbe sealed against exposure to the primary coolant water. However,advantageously, the connectors 42, 52 themselves can be immersed inwater. This makes installation, to be further described, readilyperformed even with the reactor core immersed in primary coolant.

FIG. 7 shows the mating electrical connectors 42, 52 of the distributionplate 22 and CRDM/standoff assembly flange 46, respectively. The femaleelectrical connector 52 (with sockets 48A) of the standoff assembly 24lowers onto and covers the male electrical connector 42 of thedistribution plate. The connectors 42, 52 preferably include glands orother features to prevent ingress of water to the mineral insulation ofthe MI cables 30, 80 at the junctions of these cables with therespective connectors 42, 52. For example, a glass seal or crushed metalseal may be employed. In this way, the connectors 42, 52 can be matedunderwater without exposing the mineral insulation, so as to facilitateinstalling the CRDM/standoff assembly at the connection site of thedistribution plate 22 while keeping the reactor core and thedistribution plate 22 submerged in primary coolant. To ensure a goodelectrical connection, the connection between connectors 42, 52 can bepurged to evacuate any trapped water. Alternatively, the electricalconnectors could be mated and not purged, albeit typically with someincreased resistance due to wet connectors.

The connector body has integrated features in both the receptacle andsocket for the brazing of the MI cable directly to them. The connectorbody also has fill holes to allow for insulation packing after the MIcable is spliced to it. The receptacle housings weld-on base is designedsuch that the entrance angle of the MI cable can be adjusted for. Thesocket housing also has integrated purge lines for the insertion of theinert gas.

Alignment features are integrated into both the receptacle and socketthat engage before the pin and sockets to ensure alignment and minimizestress. These alignment features optionally include a compliance featuresuch as a wave spring to help in allowing for multiple degrees offreedom with the sockets when mating.

Alternatively, an elastomer component can be used to drive water out ofany voids instead of purging with an inert gas. Multiple MI cables canbe routed to a single connector instead of a single connector feeding asingle MI cable.

FIG. 8 is an enlarged isolation perspective view of the connector 42that is mounted in the distribution plate 22. Visible are the five maleprongs 48B, which in some embodiments are gold-plated pins to reduceelectrical contact resistance, penetrating a glass seal plate 49. Thehermetically sealed connector formed by the prongs 48B and seal plate 49may in general be a sealed glass connector, sealed ceramic connector, asealed glass ceramic connector, or so forth. The connector has a trunk64 that houses the splice or brazing to the MI cable.

FIG. 9 shows an alternative embodiment of the connector. The connector66 corresponds to the connector 52 of the earlier embodiment, butterminates a single MI cable 80. Connector 66 has a purge line 70 topump in an inert gas such as nitrogen or argon to evacuate any liquidwhen mating to connector 67. MI cable 80 is connected to connector 66via a splicing sleeve 68. The purge line 70 may be alternatively locatedon the lower connector.

FIG. 10 shows a connector 66 installed in the boss or collar 53 incutaway. Purge line 70 runs into the area between the connectors,allowing the connection to be purged of fluid. The external connectionto the purge line 70 optionally comprises a self-sealing connector orother mechanism enabling the purge line 70 to be sealed off afterpurging so as to trap residual purge gas in the space between theconnectors and prevent water ingress after the purging. The femaleconnector 76 mounted in the distribution plate 22 corresponds to theconnector 42 of the previous embodiment. Connector 66 on the standoffhas a male extension 74 extending from the connector 66 down into thefemale connector 76 to make the mating.

FIGS. 11 and 12 show exploded and assembled perspective isolation views,respectively, of the connectors 66 and 76 of the standoff assembly anddistribution plate, respectively. The extending portion 74 of theconnector 66 extends down into connector 76. Connector 76 is formed ofthree parts: a top part 76A, a MI cable weld prep part 76B, and anadjustable weld-on base 76C. The top part 76A receives connectorextension 74. The MI cable weld prep portion 76B receives the MI cableand allows the cable to be welded in place. The adjustable weld on baseis welded into place, protecting the junction of the MI cable conductorsto the top portion. Instead of or in addition to a welded metallic seal,other sealing configurations such as a glass-to-metal seal or a crushedmetal seal may be employed. FIG. 12 also illustrates a wave spring 77optionally used to provide compliance when connecting the connectors 66,76.

FIG. 13 diagrammatically illustrates a method of connecting a CRDM to astandoff to form a preassembled CRDM/standoff assembly and thenconnecting the CRDM/standoff assembly to the distribution plate. In stepS1310, the method starts. In step S1320, the CRDM is bolted to thestandoff assembly by a plurality of bolts. In step S1330, the electricalcable(s) are connected the electrical connection(s). In step S1340, thestandoff plate, with CRDM bolted on top of it, is lowered onto thedistribution plate, with the bolt holes 50 making contact first toensure proper alignment of the standoff assembly and CRDM. In stepS1350, the hold-down bolts are installed and torqued to attach thestandoff assembly to the distribution plate and to ensure positivecontact in the hydraulic and electrical connectors. At step S1360, theelectrical connectors are optionally purged. At step S1370, the methodends.

FIG. 14 illustrates a method of removing a CRDM from a distributionplate. In step S1410, the method starts. In step S1420, the hold-downbolts are removed. In step S1430, the CRDM and connected standoffassembly are lifted away from the distribution plate. In step S1440, theCRDM is optionally removed from the standoff assembly for repair orreplacement. In step S1450, the method ends.

The disclosed approaches advantageously improve the installation andservicing of powered internal mechanical reactor components (e.g., theillustrative CRDM/standoff assembly) by replacing conventional in-fieldinstallation procedures including on-site routing and installation ofpower lines (e.g. MI cables or hydraulic lines) and connection of eachpower line with the powered internal mechanical reactor component with asimple “plug-and-play” installation in which the power lines areintegrated with the support plate and power connections areautomatically made when the powered internal mechanical reactorcomponent is mounted onto its support plate. Wet mating is enabled bythe use of sealed male and female connectors and optional purging ofspace between the joined male and female connectors. The disclosedapproaches leverage the fact that most powered internal mechanicalreactor components are conventionally mounted on a support plate inorder to provide sufficient structural support and to enable efficientremoval for servicing (e.g., a welded mount complicates removal forservicing). By modifying the support plate to also serve as a powerdistribution plate with built-in connectors that mate with matingconnectors of the powered internal mechanical reactor component duringmounting of the latter, most of the installation complexity is shiftedaway from the power plant and to the reactor manufacturing site(s).

The example of FIGS. 1-14 is merely illustrative, and numerousvariations are contemplated. For example, the CRDM/standoff assembly canbe replaced by a CRDM with an integral mounting flange, that is, thestandoff can be integrally formed with the CRDM as a unitary element(variant not shown).

With reference to FIGS. 15 and 16, as another illustrative example thedisclosed approaches are applied to internal reactor coolant pumps(RCPs) 1400, such as are disclosed in Thome et al., U.S. Pub. No.2010/0316181 A1 published Dec. 16, 2010 which is incorporated herein byreference in its entirety. For placement of the internal RCPs 1400 inthe cold leg (i.e. the downcomer annulus), the RCPs 1400 are envisionedto be mounted on an annular pump plate 1402 disposed in the downcomerannulus. The pump plate 1402 serves as structural support for the RCPs1400 and also as a pressure divider to separate the upper suction volumeand the lower discharge volume. In the illustrative embodiment there areeight connection sites with six of these shown in FIG. 14 as containingRCPs 1400, and the remaining two being unused to illustrate theconnection sites. The pump plate 1402 is modified to include MI cables1404, 1405 disposed in or on the pump plate 1402. The annular shape ofthe pump plate 1402 precludes long straight runs of MI cable; however,the illustrative MI cables 1404, 1405 are oriented circumferentiallywith a large bend radius comparable with (half of) the inner diameter ofthe pressure vessel 11. Bolt apertures 1440 and electrical connectors1442 are analogous to bolt apertures 40 and electrical connectors 42 ofthe illustrative CRDM embodiment, respectively. The opening 26 of theconnection site of distribution plate 22 translates in the pump plate1402 to be a generally circular opening 1426 (optionally keyed by asuitable keying feature, not shown) through which the RCPs 1400 pumpprimary coolant downward.

As yet another contemplated modification, it will be appreciated thatthe female connector can be located in the supporting power distributionplate while the male connector can be located in the flange, standoff orother mounting feature of the internal mechanical reactor component.

The preferred embodiments have been illustrated and described.Obviously, modifications and alterations will occur to others uponreading and understanding the preceding detailed description. It isintended that the invention be construed as including all suchmodifications and alterations insofar as they come within the scope ofthe appended claims or the equivalents thereof.

We claim:
 1. A method comprising: providing an internal control roddrive mechanism (CRDM) including an electric motor and a support surfaceincluding sealed electrical connectors electrically connected with theelectric motor to deliver electrical power to the electrical motor;installing the internal CRDM inside a nuclear reactor, the installingincluding placing the support surface of the internal CRDM onto asupport element inside the nuclear reactor, the placing causing sealedelectrical connectors disposed on the support element to mate with thesealed electrical connectors on the support surface of the internalCRDM; wherein the nuclear reactor contains coolant water and theinstalling is performed with the internal CRDM submerged in the coolantwater and the seals of the sealed electrical connectors of the internalCRDM and the support element are effective to prevent coolant wateringress into the sealed electrical connectors.
 2. The method of claim 1wherein the providing comprises: welding the connector elements ontoends of mineral-insulated cables (MI cables) providing power to theelectric motor to form the sealed electrical connectors of the internalCRDM.
 3. The method of claim 1 wherein the installing further comprises:after the placing is performed, purging space between the mated sealedelectrical connectors of the internal CRDM and the support elementthrough a purge line using an inert gas.
 4. The method of claim 3wherein the installing further comprises: sealing off the purge lineafter the purging to trap residual inert gas in the space between themated sealed electrical connectors of the internal CRDM and the supportelement.
 5. The method of claim 1 wherein the sealed electricalconnectors of the internal CRDM and the support element are sealed glassconnectors, sealed ceramic connectors, or sealed glass ceramicconnectors.
 6. The method of claim 1 wherein the installing furthercomprises: during the placing, providing compliance springs betweensealed electrical connectors disposed on the support element and themating sealed electrical connectors on the support surface of theinternal CRDM.
 7. An apparatus comprising: an internal control rod drivemechanism (CRDM) including as a unitary assembly: an electric motor, asupport surface, sealed glass, ceramic, or glass-ceramic electricalconnectors disposed on the support surface, and mineral insulated (MI)cables extending from the electric motor and having ends sealed insidethe sealed glass, ceramic, or glass-ceramic electrical connectors. 8.The apparatus of claim 7, wherein the seals of the sealed glass,ceramic, or glass-ceramic electrical connectors are effective to allowthe internal CRDM to be immersed in water without water ingress into theMI cables.
 9. The apparatus of claim 7, wherein each sealed glass,ceramic, or glass-ceramic electrical connector further includes a purgeline arranged to admit purge gas into space between the sealed glass,ceramic, or glass-ceramic electrical connector and an associated matingconnector.
 10. The apparatus of claim 7, further comprising: adistribution plate with pass-through openings and sealed glass, ceramic,or glass-ceramic electrical connectors disposed on the distributionplate; wherein the support surface of the internal CRDM is configured tobe placed onto the distribution plate with its connecting rod passingthrough a pass-through opening of the distribution plate and its sealedglass, ceramic, or glass-ceramic electrical connectors mating withsealed glass, ceramic, or glass-ceramic electrical connectors disposedon the distribution plate.
 11. The apparatus of claim 7, wherein one of(i) each sealed glass, ceramic, or glass-ceramic electrical connector ofthe internal CRDM and (ii) each sealed glass, ceramic, or glass-ceramicelectrical connector disposed on the distribution plate further includesa purge line arranged to admit purge gas into space between the sealedglass, ceramic, or glass-ceramic electrical connector and an associatedmating connector.
 12. The apparatus of claim 7, further comprising: adistribution plate with pass-through openings and sealed glass, ceramic,or glass-ceramic electrical connectors disposed on the distributionplate, the support surface of the internal CRDM being disposed on thedistribution plate with its connecting rod passing through apass-through opening of the distribution plate and its sealed glass,ceramic, or glass-ceramic electrical connectors mating with sealedglass, ceramic, or glass-ceramic electrical connectors disposed on thedistribution plate; and a spring disposed between each sealed glass,ceramic, or glass-ceramic electrical connector of the internal CRDM andits mating sealed glass, ceramic, or glass-ceramic electrical connectordisposed on the distribution plate.